Radial piston pump



Dec. 3, 1968 E. COOK ET AL. 3,413,929

RADIAL PISTON PUMP Filed April 21, 1966 2 Sheets-Sheet 1 2 INVENTORS458M557 5. Cook BY RA/wa 'Bm 4 rrozvers 88 FIE: E

Dec. 3, 1968 E. E. COOK ET AL. 3,413,929

RADIAL PISTON PUMP Filed April 21. 1966 2 Sheets-Sheet 2 9 /0 I300 O I IIZOa 120 Zia/5:7 62 600k BY AMQIY PAPEJA Patented Dec. 3, 1968 3,413,929RADIAL PISTON PUMP Ernest E. Cook, Anoka, and Ramon Pareja, Edina,Minn.,

assignors to Hypro, Inc., Minneapolis, Minn., a corporation of OhioFiled Apr. 21, 1966, Ser. No. 544,129 4 Claims. (Cl. 103-174) ABSTRACTOF THE DISCLOSURE A radial piston pump having a plurality of cylindersfunctioning in combination with an inlet chamber and an outlet chamber,the inlet and outlet chambers being disposed generally co-axially, onewith another, the outlet chamber being circumscribed about the peripheryof the inlet chamber. Appropriate valving, including valving extendingradially through the pumping pistons is employed for the inlet to thecylinders, and check valve means, arranged along the inner axis portionof the pistons is employed to control fiow during the outlet or pressurestroke. Check valve means are also provided to isolate the pumpingcylinders from the pressure chamber. The pistons are driven by aneccentric means, and have a tapered base portion in order to reduce theaxial drive width requirement.

This invention relates to hydraulic pumps, and more particularly to ahydraulic pump of the radial piston type in which a plurality ofradially directed pistons operate to pump fluid radially outwardly froman inner suction chamber toan outer pressure chamber.

An object of the present invention is to provide a pump of the characterdescribed which has relatively high volume and pressure efliciency,while being relatively simple and compact mechanically.

Another object of the present invention is to provide a pump of thecharacter described which is easy to assemble and in which all of theparts are readily accessible for servicing. A related object of theinvention is the provision of a radial eccentric drive mechanism for apump of the character described which is simple in construction and easytoassemble, and in which lubrication of the various moving parts isreadily accomplished.

It is another object of the invention to provide a pump of the characterdescribed in which the various piston and cylinder assemblies thereofare provided with an improved bearing and sealing arrangement so that nointernally lapped surfaces are required in the cylinders.

It is another object of the invention to provide a pump of the characterdescribed in which the arrangement of the pistons and cylinders is suchthat any fluid which does leak from the pressure side of the pump willreturn to the suction side thereof, so that in the event that apre-mixed substance is being pumped there will be no variation in thebalance thereof.

Briefly described, the pump according to the invention includes a pumphousing having a suction chamber, a pressure chamber, and an opencentral drive chamber inwardly of the suction chamber. The central drivechamber houses an eccentric drive mechanism, which is internallylubricated so that no enclosure or sealing means for the central drivechamber is required. The suction chamber and the pressure chamber arecoupled or joined by a plurality of radially directed pump cylinders,having radial pistons moving therein under the action of the eccentricdrive mechanism. The various pistons are guided within the cylinders onself-lubricating bearings, and improved sealing means are provided toprevent flow of fluid past the exterior surfaces of the pistons. Fluidflow is through passages in the body of each piston, and valvingincluding an inertial ball check valve in the piston is provided for thepump action.

Other objects, advantages and new features of the invention will becomeapparent from a reading of the following detailed description when readin conjunction with the accompanying drawings, wherein:

FIGURE 1 is an elevational view of a pump constructed in accordance withthe invention. illustrating especially the open central drive chamberthereof;

FIGURE 2 is a sectional view through the pump, taken on the line 22 ofFIGURE 1;

FIGURE 3 is a sectional view taken on the line 3-3 of FIGURE 2; and

FIGURE 4 is a detailed sectional view through one of the pump cylinders,taken on the line 4-4 of FIG- URE 3.

In the illustrated embodiment of the invention, the pump is generallyindicated at -10 and consists of .a cast body 12 adapted to be mountedin any suitable fashion adjacent a motor or the like, not shown. Formedcentrally in the body, 12 are a pair of cylindrical surfaces 14 and 16,separated by an internal flange 18, these elements defining a centraldrive chamber 20, in which is disposed the eccentric drive mechanism 2.2of the present pump.

Eccentric drive mechanism 22 includes a main drive shaft 24 which isjournaled for rotation on a suitable ball bearing element 26 within thesurface 16, shaft seal 28 being provided between the inner surface 27 ofthe flange 18 and the drive shaft 24, as shown. An eccentric shaft 30 isformed, as by machining, on the main drive shaft 24, and carries aroller bearing assembly 32 mounted in surrounding relation thereto.Roller bearing assembly 32 has a circular outer peripheral surface 34which acts during rotation of drive shaft 24 as a cam for reciprocatinga plurality of pump pistons 35, which have elongated cylindrical bodies35a guided for reciprocating motion in a plurality of radially orientedpumping stations 36. While the pump of the illustrated embodiment hasibeen shown as having four such pumping stations 36, it will beunderstood that more or fewer pumping stations may be employed. Adiametrically opposed relationship of pumping stations is preferred,however, because of the manner in which the pistons 35 are associatedwith the roller bearing assembly 32.

Each of the pistons 35 has a fiat surface 38 thereon which is adapted tobe engaged by the peripheral surface 34 of the roller bearing assembly32. The surfaces 38 on each of the diametrically opposed pairs ofpistons 35 are held firmly at a spacing substantially equal to thediameter of the roller bearing assembly 32 by means of a couplingelement 40, which is generally C-shaped so as to clear the rotatingparts of the eccentric drive mechanism 22. Pistons 35 and couplingelements 40 are shaped in complementary position to provide the desiredspacing between the surfaces 38. Thus, the pistons are provided with atapered portion 41 and a head 42 separated y a short cylindrical portion44 of reduced diameter, as

3 shown. It will be apparent that the head 42 and the short cylindricalportion 44 on each of the pistons define a shoulder disposed at apredetermined distance from the surface 38 on each piston.

The coupling elements 40 are provided adjacent each of their ends withmeans for engaging the pistons behind the respective shoulders 45, sothat inward motion of the coupling elements 40 will draw the pistons 35inwardly. As best seen in FIGURE 2, the coupling elements 40 areprovided with angled end portions 46 which are slotted as indicated at48 to conform to the shape of the tapered portion 41 and the shortcylindrical portion 44 of the pistons 35. With the pistons disposed inslots 48, the inner surfaces on the portions 46 of the connectingelement 40 will engage the shoulders 45 to establish the positions ofthe pistons with respect to the coupling element 40. To retain eachpiston in its slot 48, a fastener, such as a bolt 51, is threadedlyengaged in the end portions 46 across the slot 48 as shown. It will benoted that because of the tapered portions 41 and the smaller headportions 42 a very compact assembly is achieved, less axial space beingrequired within the central drive chamber 20 than would be required ifthe pistons 35 were of uniform diameter.

It will be noted in FIGURE 2 that the two pistons 35 which appear inthat figure are not centered on the roller bearing assembly 32, but areoffset to the right side thereof. The other two pistons 35 which are at90 to the position show in FIGURE 2 engage the bearing assembly 32 atthe left side thereof, so that the axes of the two opposed pairs ofpistons are spaced from one another. This arrangement allows the angledend portions 46 of each of the coupling elements 40 sufficient room toclear the other coupling element 40 during rotation of the parts.

Because the pistons 35 can only move axially of themselves within theirrespective pumping stations 36, the surfaces 38 of the pistons 35 willslip with respect to the surface 34 as the roller bearing assembly 32 isrotated. Provision is made in the present embodiment for lubricatingsurfaces 38 and 34 from within the bearing 32. Thus, the eccentric shaft30 is provided with an axial fluid passage 52 and a radial passage 54which communicates through an annular recess 55 in the bearing 32 with aplurality of radially directed lubricant passageways 56 extending out tothe peripheral surface 34 of the roller bearing assembly 32. A greasefitting 58, threadedly engaged in the end of eccentric shaft 30, is incommunication with the lubricant passage 52 so that a grease gun or thelike may be applied to the fitting to supply lubricant through thepassages 52, 54 and 56 to the surface 34.

'Means defining a pump cylinder for the accomodation of each piston 35are contained within each of the pumping stations 36. Attention isdirected to FIGURE 4 which shows the various parts to a slightly largerscale. As there shown, each of the pumping stations 36 is bounded by acylindrical bore 60 formed in the pump body 12, the cylindrical bore 60extending from the outer periphery of the body 12 and terminating justshort of the inner cylindrical surface 14. An opening 61, of slightlyless diameter than the bore 60, opens through the surface 14 and defineswith bore 60 a shoulder 62 acting as a stop shoulder for the variouscylinder defining parts within the bore 60.

Piston 35 is guided for reciprocating movement in spaced annularbearings 64 and 65, which are of the selflubricating type. A compositesupporting structure is provided for the bearings 64 and 65 so that allthe parts may be conveniently assembled by inserting them into the bore60 from the outer end thereof. The supporting elements for the bearingsconsisting of a pair of sleeves 66 and 68 and a cup-shaped element 70.

Sleeve 66 fits within the cylindrical bore 60 and has a terminalprojection 71 of smaller diameter which projects through the opening 61,a shoulder 72 adjacent projection 71 defining the innermost position ofsleeve 66. Internally, sleeve 66 has a counterbored configuration toprovide, first, an opening 74 for the accommodation of piston 35.Adjacent the opening 74, sleeve 66 has a slightly larger bore 75 inwhich is disposed the bearing 64. It should be noted that bore 75 alsohouses an annular packing element 76 which is made of a wear-resistantmaterial and which is held in place by an O-ring 78 which is disposed inencircling relation therearound in the manner of a garter spring.

Sleeve 68 fits within the next larger cylindrical bore 80 within thesleeve 66, the end 68a thereof resting against a shoulder 81 between thebores 75 and 80 to retain the bearing 64, and packing element 76 and theO-ring 78 within the bore 75. Cup-shaped element 70 retains bearing 65and a second packing element 82, held by an O- ring 84, adjacent theopposite and 68b of sleeve 68 as shown.

Piston 35 is in its outermost radial position in FIG- URE 4, but it willbe seen in FIGURE 2 at the top that the cylindrical inner surfaces 85and 86 of the bearing elements 65 and cup-shaped elements 70,respectively, are such as to define a space 87 above the end of thepiston when it is in its retracted position.

Within the outer end of bore 60 is a check valve assembly 88, which hasa spool shaped supporting body 90 fitting within the cylinder 60. Body90 is internally hollow and has a shoulder 91 formed therein whichretains a valve seat element 92 having a central passage 94 incommunication with the space 87. An outwardly tapered valve seat 95 isformed in the element 92, and a valve element 96 rests against the valveseat 95 during the suction stroke of the piston 35 and is lifted awayfrom the seat by fluid pressure during a pumping stroke thereof. Aspring 98 reacts between the body 90 and the valve element 96, suitablebosses 100 and 101 being provided on these elements respectively toposition the respective ends of spring 98.

All the parts which have been described as being within the bore 60 areheld in their assembled relation by means of a plug 102 which isreceived in the threaded outer end 104 of the cylinder 60. VariousO-ring seals may be employed where desired between the parts, referencenumerals having been omitted from the seals shown for purposes ofclarity.

Each of the pistons 35 has fluid passage means therein for allowingfluid to pass to the pumping space 87 during a suction stroke of thepiston 35. Thus, each piston body 35a is provided with radial bores 105,disposed intermediately of the ends thereof, and respective axial bores106 and 108, the latter opening through the end of the piston 35. A ballcheck valve retaining cage 109 is disposed in the bore 108 and houses aball 110 which, in the operation of the pump, rests alternately againsta seat 111 formed between the bores 106 and 108 and against a closuredisc 112 which is held within the piston 35 by means of a suitableretaining ring 114. An aperture 115 in the closure plate 112 permitsfluid to flow from the bore 108 into the space 87 during a suctionstroke of piston 35.

The radial bores 105 in the various pistons 35 are in continuous fluidcommunication with the inlet or suction side of the pump. As bestillustrated in FIGURE 3, the body 12 of the pump is provided with aninlet port 116 which is defined by an internally threaded boss 118which, it will be understood, may be utilized to couple the pump to asuitable fluid conduit. The inlet port 116 communicates with a suctionchamber 120, which is in turn in communication with the radial bores 105in the pistons 35 through apertures 121 opening into the cylindricalbores 60 and through openings 122 and 123 in the sleeves 66 and 68,respectively.

An annular recess 124 is provided in each sleeve 66 so that fluid may beby-passed around the pumping stations 36 which are adjacent the inletport 116 to the pumping stations 36 which are remote therefrom. Thesleeve 68 is also provided with an annular recess, 125, the axial lengthof which is such that-the openings 105 in the pistons 35 are incontinuous fluid communication with the suction side of the pump asstated above. The portions of the suction chamber extending to the tworemote pumping stations 36 have been designated 120a in FIGURE 3.

The outlet port of the pump is indicated at 126 and is defined by aninternally threaded boss 128 which is similar to the boss 118. Outletport 126 communicates with a pressure chamber 130, which is in fluidcommunication with each of the pump cylinders 36- through openings 131and annular recesses 132 defined by the spool shaped check valveassemblies 88. Passages 130a link the cylinders 36 which are adjacentthe pressure chamber 130 with those which are remote therefrom in amanner similar to the suction chamber portions 120a.

The operation of the present pump should be apparent from the foregoingdescription of its structure; however, the following summary is providedto aid in the understanding of the invention. First, it will beunderstood that the pump will be connected to suitable fluid conduitsthreadedly engaged with its bosses 118 and 128. Upon rotation of themain drive shaft 24, the eccentric assembly 32 will be rotated toreciprocate the various pistons 35 within their associated cylinders.

The ball 110 responds to the flow of fluid within each of the pistons 35so as to be pressed against the valve seat 111 during an outward strokeof the piston and raised ofl the valve seat 111 during an inward strokethereof. The inward stroke] is, of course, the suction stroke duringwhich the space 87 is created by the withdrawal of the piston.Retraction of the piston 35 thus results in outward flow of fluid whichlifts the ball 110 off seat 111 and permits fluid to pass up from theaxial bore 106, past the ball 110, into the chamber '87. Upon outwardmotion of the piston 35, the ball 110 will move back against the valveseat 111 and the fluid in the chamber 87 will therefore be confined andput under pressure by the outward travel of the piston 35. The pressureimposed on the fluid will then lift the valve element 101 off its seatagainst the action of the spring 98 to permit the fluid to pass to thepressure chamber 130 of the pump and from there to the outlet port 126.

The arrangement of the pistons with their through passageways and thecheck valves therewithin is such that the volumetric efiiciency of thepresent pump is quite high and the tight seal provided by the ball checkelement when against the seat 111 provides for good pressure efliciency.The eccentric drive mechanism for the pump when coupled with theexcellent bearing supportfor the various piston 35, and with the uniquecoupling means for holding the pistons 35 at the desired spacing providefor efficient mechanical operation. Wear has been reduced to a minimumso that the average liftime of the parts has been increased.

It should now be apparent that a pump has been described which fulfillsall of the objects set forth hereinabove. It will be understood, ofcourse, that the invention is not limited to the specific form orarrangement of parts shown.

We claim:

1. A radial piston pump comprising a housing, means defining an inletport and an outlet port in said housing, means defining an inlet chamberin communication with said inlet port, a pressure chamber disposedcoaxially with and generally circumscribing said inlet chamber and incommunication with said outlet port and an open central drive chamberdisposed generally coaxially with said chambers and within said housing,means defining a plurality of mutually opposed pump cylinders coupled tosaid inlet chamber and to said pressure chamber, said pump cylindersbeing radially disposed with respect to a central axis within saidhousing, a piston disposed in each of said pump cylinders and having aportion thereof extending into said central drive chamber, eccentricdrive means mounted in said drive chamber for rotation about saidcentral axis, means holding each of said pistons in contact with theperiphery of said eccentric drive means to be reciprocated thereby,first and second passage means in each of said pistons, said firstpassage means having a portion thereof radially directed with respect tothe axis of-said piston extending through said piston andin continuousuninterrupted communication with said inlet chamber during reciprocationof said piston and said second passage extending generally axially ofsaid piston between said radial passage means and the free outer end ofsaid piston, a check valve in each of said pistons within said secondpassage for allowing fluid to pass through said passage means during aninward stroke of said piston and for preventing flow with respect tosaid piston during an outward stroke thereof, and check valve meansbetween each cylinder and said pressure chamber for permittingunidirectional flow outwardly from said cylinder to said pressurechamber, each of said pistons having an elongated cylindrical bodywithin each of said cylinders, said inlet chamber communicating witheach piston immediately of the ends of said elongated cylindrical body,each cylinder defining means including spaced bearing means engagingsaid piston body radially inwardly of and radially outwardly of saidinlet chamber for supporting said piston for sliding movement in saidcylinder, and packing means adjacent each bearing means for preventingleakage of fluid between said piston and said cylinder.

2. A radial piston pump comprising a housing, means defining an inletport and an outlet port in said housing, means defining an inlet chamberin communication with said inlet port, a pressure chamber disposedcoaxially with and generally circumscribing said inlet chamber and incommunication with said outlet port and an open central drive chamberdisposed generally coaxially with said chambers and within said housing,means defining a plurality of mutually opposed pump cylinders coupled tosaid inlet chamber and to said pressure chamber, said pump cylindersbeing radially disposed with respect to a central axis within saidhousing, a piston disposed in each of said pump cylinders and having aportion thereof extending into said central drive chamber, eccentricdrive means mounted in said drive chamber for rotation about saidcentral axis, means holding each of said pistons in contact with theperiphery of said eccentric drive means to be reciprocated thereby,first and second passage means in each of saidpistons, said firstpassagerneans having a portion thereof radially directed with respect tothe axis of said piston extending through saidf-piston and in continuousuninterrupted communication 'with said inlet chamber duringreciprocation of said piston and said second passage extending generallyaxially of said piston between said radial passage means and the freeouter end of said piston, a check valve in each of said pistons withinsaid second passage for allowing fluid to pass through said passagemeans during an inward stroke of said piston and for preventing flowwith respect to said piston during an outward stroke thereof, and checkvalve means between each cylinder and said pressure chamber forpermitting unidirectional flow outwardly from said cylinder to saidpressure chamber, the check valve means between each cylinder and thepressure chamber being disposed Within a retaining member having anouter annular recessed zone for providing continuous access and flowalong the extent of said pressure chamber.

3. A radial piston pump as defined in claim 1, wherein said bearingmeans are made of self-lubricating material.

4. A radial piston pump as defined in claim 1, wherein said packingmeans comprise annular rings of wear-resistant material.

(References on following page) References Cited UNITED STATES PATENTSPardee 103-174 Cornrelius et a1. 230-187 Borgerd et a1. 230-187 Sewell103-174 Gaarder 103-204 8 3,011,845 12/1961 Watt et al 92-155 3,174,4363/1965 Wanner 103-174 FOREIGN PATENTS 5 584,121 2/1958 Italy.

WILLIAM L. FREEH, Primary Examiner.

Patent No. 3,413,929 December 3, 1968 Ernest E. Cook et a1.

ied that error appears in the above identified It is certif tters Patentare hereby corrected as patent and that said Le shown below:

"and? should read end Column 6,

Column 4, line 18,

d intermediately line 24, "immediately" should rea Signed and sealedthis 10th day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, J r.

Commissioner of Patents Attesting Officer WILLIAM E. SCHUYLER, IR.

